1. Field of the Invention
The present invention generally relates to the dissipation of operating heat in electronic devices such as computers and, in a preferred embodiment thereof, more particularly provides a computer in which component operating heat is conducted to an evaporator portion of a heat pipe having a condenser portion forming the shroud section of an axial heat dissipation fan.
2. Description of Related Art
Portable computers, such as the ever popular compact notebook computer, present unique component-cooling problems. For example, as notebook computers become more powerful and sophisticated their small base housings are being more densely packed with faster and considerably hotter operating components such as processors, drives, AC/DC converters, modems and the like. The prime portable computer requirement for compactness is thus becoming a greater and greater barrier to meeting the critical requirement to effectively dissipate component operating heat generated in the base housing. Heat must be moved away from these internal components to keep their maximum temperatures low enough to prevent thermal overload failures thereof.
Without forced ventilation, this internal operating heat must be dissipated at the computer's external surfaces. Of course, more operating heat can be dissipated to ambient by increasing the exterior surface area or permitting the exterior computer surface area to reach a higher temperature during operation of the computer. However, the exterior surface area available for heat transfer is limited by the computer's size (which must be kept compact), and the allowable maximum exterior surface temperature of the computer is limited by the comfort of the user, who is likely to be in close physical contact with the computer while it is operating. Spreading of the heat to the various external surfaces, by conduction or by using thermosyphoning heat pipes, is helpful in this regard but presents difficult technical challenges.
Forced ventilation using fans is commonly employed for all manner of larger electronic products including computers of desktop and larger sizes (i.e., considerably larger in internal volume than portable computers). These products lend themselves well to such cooling because physical room is available both for internal cooling passages and for the mounting of adequate capacity fans. Fan ventilation has also been used for portable computers, but generally with poor efficiency owing to the major compromises with respect to available internal cooling air paths. Compactness dictates that internal components and circuit boards be packed as tightly as possible, a situation that unavoidably reduces the size and number of interior passages through which cooling air can be routed.
In order to overcome the various portable computer cooling problems outlined above, various cooling systems have been previously proposed in which thermosyphoning heat pipes are used in combination with fans. These methods are not unique to small computers, but have been adapted to them from other cooling applications.
One previously proposed approach to using a heat pipe in a forced air cooling application in a portable computer has been to mount a cooling fan in a side wall of the computer housing so as to discharge air outwardly therethrough, and place a condenser end portion of a heat pipe, with cooling fins thereon, outwardly adjacent the inlet to the fan. An evaporator portion of the heat pipe was placed in thermal communication with a heat generating component within the computer housing.
The main disadvantages of this previously proposed approach are the relative remoteness of the heat pipe condenser portion from the fan, the relative inefficiency of the fins, and the space inefficiency of having to dedicate housing volume to both the fan and the associated separate cooling fin structure.
From the standpoint of the heat pipe condenser portion being remote from the fan, the air flow through the fins is primarily laminar. This feature is designed into the system to promote fan and air flow efficiency, but results in a penalty in efficiency as to the overall heat transfer efficiency of the cooling system. The thermal inefficiency of the fins themselves arise from the fact that, in general, the portions of the fins most distant from the heat pipe condenser portion are relatively cool and are thus less effective in transferring heat to the moving cooling air. These fin portions accordingly obstruct cooling air flow but provide relatively low heat transfer thereto.
From the foregoing it can be seen that a need thus exists for an improved heat pipe-based forced air cooling system for a portable computer. It is to this need that the present invention is addressed.